NIOS Class 12 Environmental Science Chapter 20
INTEXT QUESTIONS 20.1
1. Define “green revolution”.
Ans: Rapid growth in food grain production from using seeds of high-yielding varieties is termed as Green Revolution. In other words, it is a substantial increase in new crop varieties of wheat and rice using large quantities of fertilisers, pesticides and good irrigation.
2. How was “Sharbati Sonora” produced by Dr Swaminathan?
Ans: A cross between semi-dwarf Mexican wheat (high-yielding and responded to fertiliser and irrigation) and Indian wheat (disease-resistant and good grain quality) resulted in high-yielding and disease-resistant varieties of wheat such as ‘Kalyan Sona’, ‘Sonalika’ and ‘Sharbati Sonora’, etc.
3. Define fertilizer.
Ans: Fertilisers are substances that are generally applied to the soil to promote the healthy growth of plants.
4. What are the advantages of using organic fertilizers or manure?.
Ans: Organic fertilisers are environmentally friendly and enrich the soil with nutrients, and improve the overall quality of the soi,l like soil texture, soil aeration and water holding capacity.
INTEXT QUESTIONS 20.2
1. What are the advantages of using disease-resistant varieties of seeds?
Ans: Disease-resistant and pest-resistant seeds will not require so much pesticide, which will save environmental pollution also save money which would have gone into the purchase of pesticides.
2. What are the functions of combine harvesters, ploughs and land levellers?
Ans:
- A combine harvester is a large farm machine that both cuts the corn and separates the grains from the ear of the plant, right in the field.
- Plough or till the soil mechanically, turning the soil over.
- Land levellers level the soil after breaking big chunks of soil or clay, and prepare the soil for sowing.
3. Of what significance is the production of seed varieties resistant to salinity, dry or waterlogged conditions?
Ans: It helps tp grow plants under various difficult situations; thereby extending the area of cultivation, e.g. dry or saline or water logged areas can be utilized for cultivation.
4. Name three important newer agricultural practices of great value and their advantages.
Ans: Mushroom culture, bee-keeping or apiculture, poultry farming are newer practices which bring money and creates employment.
INTEXT QUESTIONS 20.3
1. Name three indigenous and three foreign breeds of cows.
Ans:
- Indigenous breeds of cows are Sahiwal, Tharparkar, and Red Sindhi.
- Foreign breeds are Jersey, Brown Swiss, and Holstein-Friesian.
2. What are the main reasons for low milk yield per day for a cow in our country?
Ans: Low milk yield in our country is due to:
- Poor quality feed
- Shortage of feed and fodder
- Low milk-yielding indigenous breeds
3. Mention the causal organisms and the symptoms of the diseases like (i) foot and mouth diseases, (ii) Rinderpest and (iii) Anthrax.
Ans:
- Foot and mouth causal organisms virus- Blisters on the mouth, foot, excessive production of saliva, loss of appetite, high temperature, shivering.
- Rinderpest causal organism: Bacteria- Discharge from eyes, nostrils, loss of appetite, constipation, followed by severe diarrhoea.
- Anthrax causal organism, Bacteria- Swelling of the body, fever, reduction in milk secretion.
INTEXT QUESTIONS 20.4
1. Mention the harmful effects of administering hormones in order to increase milk production in cows.
Ans: Detrimental effect of hormones on livestock and poultry
- Indiscriminate use of hormones, used orally or injecte,d may be harmful for the animal as well as for the milk it produces.
- Hormone increases the amount of milk, but their udder enlarges abnormally, so much so that the cows have difficulty in movement and they develop an abnormal goitre.
- It also affects their normal physiology of reproduction.
- Oxytocin causes milk ejection from mammary glands in nursing mothers. This hormone also causes uterine contraction, so injection of this hormone for milk release can cause pain and discomfort to the animal.
2. Define aquaculture?
Ans: Aquaculture is the farming of aquatic organisms, including fish, molluscs, crustaceans and aquatic plants. Basically, aquaculture or fish farming involves cultivating fish in a controlled environment (coastal or inland pond, lake, or reservoir) and harvesting them when they reach the desired size.
3. Which are the main dangers the fish population suffer from?
Ans: Fish populations in the oceans of the world suffer from:
- Over exploitation
- Habitat destruction
- Incidental mortality of non-target species
- Pollution
4. What is the advantage of the system of eco-aquaculture?
Ans: Ecological aquaculture focuses on an adequate farming system that preserves the aquatic environment in which they are suited and can be harvested sustainably.
TERMINAL EXERCISE
1. Define green revolution. Which were the two crops specially involved with ‘Green Revolution’ in the beginning?
Ans: The term “Green revolution” refers to a substantial increase in grain yield obtained by plant breeders by developing new crop varieties. The high-yielding varieties (HYVs) of wheat and rice have been the key elements in the green revolution.
2. Which was the wheat variety produced by Dr. M.S. Swaminathan, and how?
Ans: ‘Sharbati, Sonara’
3. What do the farmers do when the pests develop genetic resistance to certain pesticides?
Ans: When genetic resistance occurs, farmers can use stronger doses or switch to other pesticides.
4. Define pesticides. Mention two advantages of using pesticides.
Ans: Pesticides are chemicals which have been developed to kill or control organisms called pests, which are unwanted by man, especially in agriculture. Modern pesticides increase food supplies, increase profits for farmers and are safe if used properly. Pesticides control most pests quickly and have a long shelf life, and are easily shipped and applied.
5. Write brief notes on the combined harvester, plough, land levellers, and box drill.
Ans:
- A combine harvester is a large farm machine that both cuts the corn and separates the grains from the ear of the plant, right in the field.
- Plough or till the soil mechanically, turning the soil over.
- Land levellers level the soil after breaking big chunks of soil or clay, and prepare the soil for sowing.
- A box drill is an attachment on tractors that are used for sowing seeds.
6. Name four new areas of agricultural practices. Write a short note on poultry farming.
Ans: The four new areas of agricultural practices are poultry farming, mushroom culture, apiculture and aquaculture.
Poultry farming is a term used for the rearing and keeping of birds such as fowl, ducks and hens for egg and meat. It has become popular because this is comparatively easy to start and maintain. It gives a quick return within one to six months of investments, is easily manageable and requires less space and labour. Poultry birds and their eggs are a rich source of nutrients.
Indian poultry birds provide good quality meat but produce small-sized eggs. They have natural immunity against common diseases as compared to exotic varieties bred abroad.
Common exotic birds are Leghorn, Rhode Island Red, and Cornish.
Common Indian breeds are Aseel, Chittagong, and Busra.
7. How do you define animal husbandry? Mention the food items that are provided by these animals.
Ans: The branch of agriculture that deals with breeding, feeding and care of domestic animals is called animal husbandry.
- Cows and buffalo are our chief sources of milk.
- Hens are egg-laying animals.
- Fishes, pigs, hens and goats are our major sources of meat.
8. Write the names of the causal organisms and animals affected with the following diseases
- Foot and mouth disease
- Pox
- Tuberculosis
- Anthrax
- Rinderpest
Ans:
- Foot and mouth disease: Virus in cattle.
- Pox: Virus in cows, buffaloes, sheep and goats
- Tuberculosis: bacteria in cattle.
- Anthrax: Bacteria in cattle, sheep, goats and pigs.
- Rinderpest: Bacteria in cattle.
Additional Study Materials
- Chapter 15 Biodiversity Conservation
- Chapter 16 Conservation of Other Natural Resources
- Chapter 17 Conservation of Soil and Land
- Chapter 18 Water and Energy Conservation
- Chapter 19 Origin and Concept of Sustainable Development
